Pharmaceutical Suspensions

Ostwald ripening

Changing of particle size in suspensions when subjected to temperature cycles

What is the maximum concentration of surfactants?

1%, higher leads to foaming

What 2 surfactants are used orally?

- Polysorbates (Tweens)

- Sorbitan esters (Spans)

What 3 surfactants are used parenterally?

- Polysorbates (Tweens)

- Poloxamers

- Lecitihin

What 3 things can be wetting agents?

- Surfactants

- Solvents

- Hydrophilic colloids

Hydrophilic colloids

Very small particles that coat a hydrophobic drug with a hydrophilic multimolecular layer

What 2 things can hydrophilic colloids be used for?

- Wetting agents

- Viscosity modifiers

Vs

Sedimentation layer volume

Vt

Total suspension volume

Stoke's Law

Measures velocity of sedimentation

Polysaccharides

- Acacia gum

- Xanthan gum

- Alginates

- Starch

Water-soluble celluloses

- Methylcellulose

- Hydroxyethylcellulose

- Microcrystalline cellulose

Hydrated silicates

- Bentonite

- Magnesium aluminium silicate

Floccule

Cluster of particles held together in a loose open structure

How is flocculation controlled?

- Electrolytes

- Polymers

- Surfactants